Lasing without inversion in a maser with injected atomic coherence

Shi-Yao Zhu, Marlan O. Scully, Ernst E. Fill

H. Fearn, Marlan O. Scully, Shi-Yao Zhu +1 more

Ning Lü

We show that the problem of a \ensuremath{\Lambda}-type (and also a V-type) three-level single-mode laser (maser) is isomorphic to that of a two-level single-mode laser (maser) under the conditions of energy-level degeneracy and equal decay rates. This correspondence reveals that lasing without population inversion can occur in the \ensuremath{\Lambda}-type system with or without an initial atomic coherence, and also gives immediately the master equation of the laser (maser) field. We analyze in detail the operational and noise properties of a \ensuremath{\Lambda}-type laser using a Fokker-Planck approach. We also present a vector model to visualize the population trapping and the absorption and emission processes in such a laser (maser) system.

Guo Qin Ge, Ying Wu, Xueli Luo +1 more

We have studied a laser system in which initially incoherent atoms are injected into a cavity and directly driven by a coherent pump field. Here we show that such a system can display optical bistability in the absence of population inversion. Two disconnected branches of the solutions are obtained for lasing action. They correspond to the inversion branch and inversionless branch, respectively. Also, a mechanism is proposed here to produce higher-power lasing by the inversionless laser.

Yifu Zhu

Fam Le Kien, Georg M. Meyer, Ulrich W. Rathe +3 more

The master equation for the field in the two-mode \ensuremath{\Lambda} laser with atoms injected in a superposition of their states is presented, and lasing without population inversion is studied from this vantage. An explicit expression for the steady-state photon distribution is derived under the conditions of detailed balance and no injected coherence. We study the photon statistics, as well as the decay of off-diagonal density-matrix elements and the linewidths of the two laser modes. The effect of an injected atomic coherence on the amplification of light is examined. It is shown that the interference terms in the master equation cancel the absorption terms if the field in each mode is in a coherent state and the conditions for atomic trapping are fulfilled. Numerical calculations demonstrate the buildup of lasing without inversion from the vacuum state of the field.